Surface supported cobalt catalysts, process utilizing these catalysts for the preparation of hydrocarbons from synthesis gas and process for the preparation of said catalysts

ABSTRACT

A supported particulate cobalt catalyst is formed by dispersing cobalt, alone or with a metal promoter, particularly rhenium, as a thin catalytically active film upon a particulate support, especially a silica or titania support. This catalyst can be used to convert an admixture of carbon monoxide and hydrogen to a distillate fuel constituted principally of an admixture of linear paraffins and olefins, particularly a C10+ distillate, at high productivity, with low methane selectivity. A process is also disclosed for the preparation of these catalysts.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is RE of U.S. application Ser. No. 08/377,293 filedJan. 24, 1995 abn., which is a continuation of U.S. application Ser. No.08/243,436 filed May 13, 1994, which is a continuation of U.S.application Ser. No. 08/032,916 Mar. 18, 1993 ABN, which is acontinuation-in-part of U.S. Ser. No. 881,935, filed May 11, 1992, whichwas a Rule 60 Continuation of U.S. Ser. No. 667,993, filed Mar. 12,1991, which was a continuation-in-part of U.S. Ser. No. 310,258, filedFeb. 13, 1989, which was a continuation-in-part of U.S. Ser. No.072,517, filed Jul. 13, 1987, which was a continuation-in-part of U.S.Ser. No. 046,649, filed May 7, 1987 all abandoned.

BACKGROUND AND PROBLEMS

1. Field of the Invention

This invention relates to catalyst compositions, process wherein thesecompositions are used for the preparation of liquid hydrocarbons fromsynthesis gas, and process for the preparation of said catalysts. Inparticular, it relates to catalysts, and process wherein C₁₀₊ distillatefuels, and other valuable products, are prepared by reaction of carbonmonoxide and hydrogen over cobalt catalysts wherein the metal isdispersed as a thin film on the outside surface of a particulatecarrier, or support, especially a titania carrier, or support.

2. The Prior Art

Particulate catalysts, as is well known, are normally formed bydispersing catalytically active metals, or the compounds thereof uponcarriers, or supports. Generally, in making catalysts the objective isto disperse the catalytically active material as uniformly as possiblethroughout a particulate porous support, this providing a uniformity ofcatalytically active sites from the center of a particle outwardly.

Catalysts have also been formed by dispersing catalytically activematerials upon dense support particles; particles impervious topenetration by the catalytically active materials. Ceramic or metalcores have been selected to provide better heat transfercharacteristics, albeit generally the impervious dense cores of thecatalyst particles overconcentrates the catalytically active siteswithin a reduced reactor space and lessens the effectiveness of thecatalyst. Sometimes, even in forming catalysts from porous supportparticles greater amounts of the catalytic materials are concentratednear the surface of the particles simply because of the inherentdifficulty of obtaining more uniform dispersions of the catalyticmaterials throughout the porous support particles. For example, acatalytic component may have such strong affinity for the supportsurface that it tends to attach to the most immediately accessiblesurface and cannot be easily displaced and transported to a more centrallocation within the particle. Catalyst dispersion aids, or agents arefor this reason often used to overcome this effect and obtain better andmore uniform dispersion of the catalytically active material throughoutthe catalyst particles.

Fischer-Tropsch synthesis for the production of hydrocarbons from carbonmonoxide and hydrogen is now well known, and described in the technicaland patent literature. The earlier Fischer-Tropsch catalysts wereconstituted for the most part of non-noble metals dispersed throughout aporous inorganic oxide support. The Group VIII non-noble metals, iron,cobalt, and nickel have been widely used in Fischer-Tropsch reactions,and these metals have been promoted with various other metals, andsupported in various ways on various substrates, principally alumina.Most commercial experience, however, has been based on cobalt and ironcatalysts. The first commercial Fischer-Tropsch operation utilized acobalt catalyst, though later more active iron catalysts were alsocommercialized. The cobalt and iron catalysts were formed by compositingthe metal throughout an inorganic oxide support. An important advance inFischer-Tropsch catalysts occurred with the use of nickel-thoria onkieselguhr in the early thirties. This catalyst was followed within ayear by the corresponding cobalt catalyst, 100 Co:18 ThO₂:100kieselguhr, parts by weight, and over the next few years by catalystsconstituted of 100 Co:18 ThO₂:200 kieselguhr and 100 Co:5 ThO₂:8 MgO:200kieselguhr, respectively. These early cobalt catalysts, however, are ofgenerally low activity necessitating a multiple staged process, as wellas low synthesis gas throughput. The iron catalysts, on the other hand,are not really suitable for natural gas conversion due to the highdegree of water gas shift activity possessed by iron catalysts. Thus,more of the synthesis gas is converted to carbon dioxide in accordancewith the equation:H₂+2CO→(CH₂)_(x)+CO₂; with too little of the synthesisgas being converted to hydrocarbons and water as in the more desirablereaction, represented by the equation: 2H₂+CO→(CH₂)_(x)+H₂O.

U.S. Pat. No. 4,542,122 by Payne et al, which issued Sep. 17, 1985,describes improved cobalt catalyst compositions useful for thepreparation of liquid hydrocarbons from synthesis gas. These catalystcompositions are characterized, in particular, as cobalt-titania orthoria promoted cobalt-titania, wherein cobalt, or cobalt and thoria, iscomposited or dispersed upon titania, or titania-containing support,especially a high rutile content titania. U.S. Pat. No. 4,568,663 byMauldin, which issued Feb. 4, 1986, also discloses cobalt-titaniacatalysts to which rhenium is added to improve catalyst activity, andregeneration stability. These catalysts have performed admirably well inconducting Fischer-Tropsch reactions, and in contrast to earlier cobaltcatalysts provide high liquid hydrocarbon selectivities, with relativelylow methane formation.

Recent European Publication 1 178 008 (base on Application No.85201546.0, filed: Sep. 25, 1985) and European Publication 0 174 696(based on Application No. 852011412.5, filed: May 5, 1985), havingpriority dates Apr. 4, 1984 NL 8403021 and 13.09.84 NL 8402807,respectively, also disclose cobalt catalysts as well as a process forthe preparation of such catalysts by immersion of a porous carrier onceor repetitively within a solution containing a cobalt compound. Thecobalt is dispersed over the porous carrier to satisfy the relationΣV_(p)/ΣV_(c)≦0.85 and ΣV_(p)/ΣV_(c)≦0.55, respectively, where ΣV_(c)represents the total volume of the catalyst particles and ΣV_(p) thepeel volumes present in the catalyst particles, the catalyst particlesbeing regarded as constituted of a kernel surrounded by a peel. Thekernal is further defined as one of such shape that at every point ofthe kernal perimeter the shortest distance (d) to the perimeter of thepeel is the same, d being equal for all particles under consideration,and having been chosen such that the quantity of cobalt present inΣV_(p) is 90% of the quantity of cobalt present in ΣV_(c). Theseparticular catalysts, it is disclosed, show higher C₅₊ selectivitiesthan catalysts otherwise similar except that the cobalt componentthereof is homogeneously distributed, or uniformly dispersed, throughoutthe carrier. Suitable porous carriers are disclosed as silica, alumina,or silica-alumina, and of these silica is preferred. Zirconium,titanium, chromium and ruthenium are disclosed as preferred of a broadergroup of promoters. Albeit these catalysts may provide betterselectivities in synthesis gas conversion reactions vis-a-vis catalystsotherwise similar except the cobalt is uniformly dispersed throughoutthe carrier, like other cobalt catalysts disclosed in the prior art, theintrinsic activities of these catalysts are too low as a consequence ofwhich higher temperatures are required to obtain a productivity which isdesirable for commercial operations. Higher temperature operation,however, leads to a corresponding increase in the methane selectivityand a decrease in the production of the more valuable liquidhydrocarbons.

Productivity, which is defined as the standard volumes of carbonmonoxide converted/volume catalyst/hour, is, of course, the life bloodof a commercial operation. High productivities are essential inachieving commercially viable operations. However, it is also essentialthe high productivity be achieved without high methane formation, formethane production results in lower production of liquid hydrocarbons.Accordingly, an important and necessary objective in the production anddevelopment of catalysts is to produce catalysts which are capable ofhigh productivity, combined with low methane selectivity.

Despite improvements, there nonetheless remains a need for catalystscapable of increased productivity, without increased methaneselectivity. There is, in particular, a need to provide further improvedcatalysts, and process for the use of these catalysts in synthesis gasconversion reactions, to provided further increased liquid hydrocarbonselectivity, especially C₁₀₊ liquid hydrocarbon selectivity, withfurther reduced methane formation.

3. Objects

It is, accordingly, the primary objective of this invention to fill thisand other needs.

It is, in particular, an object of this invention to provide furtherimproved, novel supported cobalt catalyst compositions, and processutilizing such compositions for the conversion of synthesis gas at highproductivity, and low methane selectivity, to high quality distillatefuels characterized generally as C₁₀₊ linear paraffins and olefins.

A further and more particular object is to provide novel, supportedcobalt catalyst compositions, both promoted and unpromoted whichapproach, or meet the activity, selectivity and productivity of powderedcatalysts but yet are of a size acceptable for commercial synthesis gasconversion operation.

A further object is to provide a process utilizing such catalystcompositions for the production from synthesis gas to C₁₀₊ linearparaffins and olefins, at high productivity with decreased methaneselectivity.

Yet another object i s to provide a process for the preparation of suchcatalysts.

4. The Invention

These objects and others are achieved in accordance with this inventionembodying a supported particulate cobalt catalyst formed by dispersingthe cobalt as a thin catalytically active film upon the surface of aparticulate support, preferably silica or titania or titania-containingsupport, especially one wherein the rutile:anatase ratio of a titaniasupport is at least about 3:2. This catalyst can be used to produce, bycontact and reaction at reaction conditions with an admixture of carbonmonoxide and hydrogen, a distillate fuel constituted principally of anadmixture of linear paraffins and olefins, particularly a C₁₀₊distillate, preferably C₂₀₊, at high productivity, with low methaneselectivity. This product can be further refined and upgraded to highquality fuels, and other products such as mogas, diesel fuel and jetfuel, especially premium middle distillate fuels of carbon numbersranging from about C₁₀ to about C₂₀.

In accordance with this invention the catalytically active cobaltcomponent is dispersed and supported upon a particulate refractoryinorganic oxide carrier, or support as a thin catalytically activesurface layer, ranging in thickness from less than about 200 microns,preferably about 5-200 microns, with the loading of the cobalt,expressed as the weight metallic cobalt per packed bulk volume ofcatalyst, being sufficient to achieve the productivity required forviable commercial operations, e.g., a productivity in excess of about150 hr⁻¹ at 200° C. The cobalt loading that achieves this result is atleast about 0.04 grams (g) per cubic centimeter (cc), preferably atleast about 0.05 g/cc in the rim also referred to as the thincatalytically active surface layer or film. Higher levels of cobalt tendto increase the productivity further and an upper limit of cobaltloading is a function of cobalt cost, diminishing increases inproductivity with increases in cobalt, and ease of depositing cobalt. Asuitable range may be from about 0.04 g/cc to about 0.7 g/cc, preferably0.05 g/cc to about 0.7 g/cc in the rim, and more preferably 0.05 g/cc to0.09 g/cc. Suitable supports are, e.g., silica, silica-alumina andalumina; and silica or titania or titania-containing support ispreferred, especially a titania wherein the rutile:anatase ratio is atleast about 3:2. The support makes up the predominant portion of thecatalyst and is at least about 50 wt % thereof, preferably at leastabout 75 wt % thereof. The feature of a high cobalt metal loading in athin catalytically active layer located at the surface of the particles,while cobalt is substantially excluded from the inner surface of theparticles (the catalyst core should have <0.04 g/cc of active cobalt),is essential in optimizing the activity, selectivity and productivity ofthe catalyst in producing liquid hydrocarbons from synthesis gas, whileminimizing methane formation.

Metals such as rhenium, zirconium, hafnium, cerium, thorium and uranium,or the compounds thereof, can be added to cobalt to increase theactivity and regenerability of the catalyst. Thus, the thincatalytically active layers, rims, or films, formed on the surface ofthe support particles, especially the titania or titania containingsupport particles, can include in addition to a catalytically activeamount of cobalt, any one or more of rhenium, zirconium, hafnium,cerium, uranium, and thorium, or admixtures of these with each other orwith other metals or compounds thereof. Preferred thin catalyticallyactive layers, rims, or films, supported on a support, notably a titaniaor a titania-containing support, thus include cobalt-rhenium,cobalt-zirconium, cobalt-hafnium, cobalt-cerium, cobalt-uranium, andcobalt-thorium, with or without the additional presence of other metalsor compounds thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plot of methane yield in the hydrocarbon synthesis productagainst productivity, vol. CO converted/vol. catalyst/hr. The closedcircles denote uniformly impregnated spheres; the open circles denotespheres impregnated only in the outer layer, the parenthetical number,indicating the thickness of the outer layer or rim.

FIG. 2 is a similar plot of methane yield in the hydrocarbon synthesisproduct against productivity. The closed circle denotes a uniformlyimpregnated sphere, the open circle a rim or outer layer impregnatedsphere with rim thickness indicated parenthetically; thetrianglesydenoting data from EPA 178008.

FIG. 3 shows high resolution imaging and EDS analysis of across-sectional view of a microtomed sample revealing the presence of anouter layer, approximately 0.5 μm thick, and rich in Al, Co and Re oncatalyst pellets of ⁻10 to 100 micron sizes. Imaging and compositionalanalysis showed that the outermost 50 nm of this layer was highlyenriched in Al, Co and Re.

A particularly preferred catalyst is one wherein the cobalt, or thecobalt and a promoter, is dispersed as a thin catalytically active filmupon titania. TiO₂, or a titania-containing carrier, or support, inwhich the titania has a rutile::anatase weight ratio of at least about3:2, as determined by ASTM D 3720-78; Standard Test Method for Ratio ofAnatase to Rutile In Titanium Dioxide Pigments By Use of X-RayDiffraction. Generally, the catalyst is one wherein the titania has arutile:anatase ratio ranging at least about 3:2 to about 100:1, orgreater, and more preferably from about 4:1 to about 100:1, or greater.Where any one of rhenium, zirconium, hafnium, cerium, thorium, oruranium metals, respectively, is added to the cobalt as a promoter toform the thin catalytically active film, the metal is added to thecobalt in concentration sufficient to provide a weight ratio ofcobalt:metal promoter ranging from about 30:1 to about 2:1, preferablyfrom about 20:1 to about 5:1. Rhenium and hafnium are the preferredpromoter metals, rhenium being more effective in promoting improvedactivity maintenance on an absolute basis, with hafnium being moreeffective on a cost-effectiveness basis. These catalyst compositions, ithas been found, produce at high productivity, with low methaneselectivity, a product which is predominantly C₁₀₊ linear paraffins andolefins, with very little oxygenates. These catalysts also provide highactivity, high selectivity and high activity maintenance in theconversion of carbon monoxide and hydrogen to distillate fuels.

The cobalt catalysts of this invention, as contrasted with (i) cobaltcatalysts, the cobalt portion of which is uniformly distributedthroughout the support particles or (ii) cobalt catalysts having arelatively thick surface layer of cobalt on the support particles, haveproven especially useful for the preparation of liquid hydrocarbons fromsynthesis gas at high productivities, with low methane formation. Incontrast with the catalysts of this invention, the prior art catalystsare found to have lower activity, and especially poorer selectivity dueto severe diffusion limitations. These catalysts (i) and (ii), supra, athigh productivities, produce altogether too much methane. Asproductivity is increased to produce greater conversion of the carbonmonoxide to hydrocarbons, increased amounts of methane are concurrentlyproduced. It was thus found that increased productivity with thesecatalysts could only be obtained at the cost of increased methaneformation. This result occurs, it is believed, because the carbonmonoxide and hydrogen reactants all too slowly diffuse through the poresof the particulate catalyst which becomes filled with a liquid product,this resulting in underutilization of the catalytically active siteslocated within the interior of the particles. Both hydrogen and carbonmonoxide must thus diffuse through the product-liquid filled pores, buthydrogen diffuses through the pores at a greater rate of speed than thecarbon monoxide. Since both the hydrogen and the carbon monoxide arereacting at the catalytic sites at an equivalent rate, a high H₂/COratio is created in the interior of the particle which leads to highmethane formation. As the rate of reaction is increased, e.g., byincorporating higher intrinsic activity or by operating at highertemperature, the catalyst becomes more limited by the rate of diffusionof the reactants through the pores. Selectivities are especially poorunder the conditions of high productivity. Thus, the catalyst usedduring a Fischer-Tropsch hydrocarbon synthesis reaction is one the poresof which become filled with the product liquid. When the CO and H₂ arepassed over the bed of catalyst and consumed at a rate which is fasterthan the rate of diffusion, H₂ progresses to the interior of theparticle to a much greater extent than the CO, leaving the interior ofthe particles rich in H₂, and deficient in CO. The formation of methanewithin the particle interior is thus favored due to the abnormally highH₂/CO ratio; an unfavorable result since CH₄ is not a desirable product.The extent to which selectivity is debited depends on the magnitude ofthe difference between the rate of diffusion and the rate of reaction,i.e., the productivity.

The catalyst of this invention is thus one wherein essentially all ofthe active cobalt is deposited on the surface of the support particles,notably the titania or titania-containing support particles, whilecobalt is substantially excluded from the inner surface of theparticles. The surface film of cobalt must be very thin and contain anadequate loading of cobalt to maximize reaction of the hydrogen andcarbon monoxide at the surface of the catalytic particle. The surfacefilm of cobalt as stated thus ranges generally from about 5 microns toabout 200 microns, preferably from about 40 microns to about 200microns, with cobalt loadings of at least about 0.04 g/cc in thecatalyst rim, preferably at least about 0.05 g/cc, more preferablyranging from about 0.04 g/cc to about 0.7 g/cc, still more preferablyfrom about 0.05 g/cc to about 0.7 g/cc, and even more preferably rangingfrom about 0.05 g/cc to about 0.09 g/cc, calculated as metallic cobaltper pack bulk volume of catalyst. The promoter metal to be effectivemust also be contained within the surface film of cobalt. If extendedinto the interior of the particle outside the cobalt film the promotermetal will have little promotional effect, if any. The metal promotershould thus also be concentrated within the cobalt film at the surfaceof the catalyst, with the weight ratio of cobalt:metal promoter, assuggested, ranging from about 30:1 to about 2:1, preferably from about20:1 to 5:1. The thickness of the surface metal film can be convenientlymeasured by an Electron Probe Analyzer, e.g., one such as produced bythe JEOL Company, Model No. JXA-50A. Cross-sections of the catalystparticles of this invention measured via use of this instrument showvery high peaks, or shoulders, at the edges of the particle across theline of sweep representative of cobalt concentration, with little or nocobalt showing within the particle interior. The edge, or “rim” of the“radially impregnated catalyst” will thus contain essentially all of thecobalt added to the catalyst. The thickness of the film, or rim, isunrelated to the absolute size, or shape of the support particles.Virtually any size particle can be employed as is normally employed toeffect catalyst reactions of this type, the diameter of the particleranging generally from about >10 microns to about 10 mm. For example,for a fixed-bed process, particle size may range from about 1 mm to 10mm and for fluidized-bed processes such as slurry-bed, ebulating-bed andfluid-bed processes from about >10 microns to about 1 mm. In a fixed-bedprocess, particle size is dictated by pressure considerations. To reducediffusion limitation effects even further, particle diameters arepreferably less than 2 mm. The particles can be of virtually any shape,e.g., as is normally employed to effect reactions for this type, viz.,as beads or spheres, extrudates, saddles or the like. By concentratingthe catalytic metal, or metals, on the extreme outer surface of theparticles, the normal diffusion limitation of the catalyst can beovercome. This new catalyst is more active in its function of bringingabout a reaction between the CO and H₂. The catalyst because of itshaving the thin layer of catalytically active metal on its surface is ineffect found to behave more ideally, approaching, in fact, the behaviorof a powdered catalyst which is not diffusion limited. However, unlikein the use of powdered catalysts the flow of the reactants through thecatalyst bed, because of the larger particle size of the catalyst, isvirtually unimpeded. Higher productivity, with lower methane selectivityis the result; a result of considerable commercial consequence. Atproductivities greater than 150 hr⁻¹ (standard volumes of carbonmonoxide converted per volume of catalyst per hour), notably from about150 hr⁻¹, preferably above about 200 hr⁻¹, at 200° C. less than 15 molepercent of the carbon monoxide converted is converted to methane,preferably less than 10 mole % converted to methane.

The catalyst of the present invention can be used in fixed-bed,slurry-bed, ebulating-bed, and fluid-bed processes. Generally thecatalyst will achieve a productivity of at least 150 hr⁻¹ at 200° C. forfixed-bed processes and at least about 1000 hr⁻¹ at 200° C. in otherthan fixed-bed processes (slurry-bed, ebulating-bed and fluid-bed). Theprocesses are limited only by the ability to remove excess heat.

In conducting synthesis gas reactions the total pressure upon the CO andH₂ reaction mixture is generally maintained above about 80 psig, andpreferably above about 140 psig. It is generally desirable to employcarbon monoxide, and hydrogen, in molar ratio of H₂:CO above about 0.5:1and preferably equal to or above about 1.7:1 to increase theconcentration of C₁₀₊ hydrocarbons in the product. Suitably, the H₂:COmolar ratio ranges from about 0.5:1 to about 4:1, and preferably thecarbon monoxide and hydrogen are employed in molar ratio H₂:CO rangingfrom about 1.7:1 to about 2.5:1. In general, the reaction is carried outat gas hourly space velocities ranging from about 100 V/Hr/V to about5000 V/Hr/V, preferably from about 300 V/Hr/V to about 2000 V/Hr/V,measured as standard volumes of the gaseous mixture of carbon monoxideand hydrogen (0° C., 1 Atm.) per hour per volume of catalyst. Thereaction is conducted at temperatures ranging from about 160° C. toabout 290° C., preferably from about 190° C. to about 260° C., and morepreferably about 190° C. to about 220° C. Pressures preferably rangefrom about 80 psig to about 600 psig, more preferably from about 140psig to about 400 psig. The product generally and preferably contains 60percent, or greater, and more preferably 75 percent, or greater, C₁₀₊liquid hydrocarbons which boil about 160° C. (320° F.).

The catalysts employed in the practice of this invention can be preparedby spray techniques where a dilute solution of a cobalt compound, alongor in admixture with a promoter metal compound, or compounds, as a sprayis repetitively contacted with the hot support particles, e.g., silica,titania, or titania-containing support particles. The particulatesupport is maintained at temperatures equal to or above about 140° C.when contacted with the spray, and suitably the temperature of thesupport ranges from about 140° C. up to the decomposition temperature ofthe cobalt compound, or compounds in admixture therewith; preferablyfrom about 140° C. to about 190° C. The cobalt compound employed in thesolution can be any organometallic or inorganic compound whichdecomposes to give cobalt oxide upon initial contact or uponcalcination, such as cobalt nitrate, cobalt acetate, cobaltacetylacetonate, cobalt naphthenate, cobalt carbonyl, or the like.Cobalt nitrate is especially preferred while cobalt halide and sulfatesalts should generally be avoided. The cobalt salts may be dissolved ina suitable solvent, e.g., water, organic or hydrocarbon solvent such asacetone, methanol, pentane or the like. The total amount of solutionused should be sufficient to supply the proper catalyst loading, withthe film being built up by repetitive contacts between the support andthe solvent. The preferred catalyst is one which consists essentially ofcobalt, or cobalt and promoter, dispersed upon the titania, ortitania-containing support, especially a rutile support. Suitably, thehot support, notably the titania support, is contacted with a spraywhich contains from about 0.05 g of cobalt/ml of solution to about 0.25g of cobalt/ml of solution, preferably from about 0.10 g of cobalt/ml ofsolution to about 0.20 g of cobalt/ml of solution (plus the compoundcontaining the promoter metal, if desired), generally from at leastabout 3 to about 12 contacts, preferably from about 5 to about 8contacts, with intervening drying and calcination steps being requiredto form surface films of the required thicknesses. The hot support, inother words, is spray-contacted in a first cycle which includes thespray contact per se with subsequent drying and calcination, a secondcycle which includes the spray contact per se with subsequent drying andcalcination, a third spray contact which includes the spray contact perse with subsequent drying and calcination, etc. to form a film of therequired thickness and composition. The drying steps are generallyconducted at temperatures ranging above about 20° C., preferably fromabout 20° C. to about 125° C., and the calcination steps at temperaturesranging above about 150° C., preferably from about 150° C. to about 300°C.

A preferred method for preparing the catalysts particles is described inPreparation of Catalysts IV, 1987, Elsevier Publishers, Amsterdam, in anarticle by Arntz and Prescher, p. 137, et seq.

Silica and titania are preferred supports. Titania is particularlypreferred. It is used as a support, either along or in combination withother materials for forming a support. The titania used for the supportis preferably one which contains a rutile:anatase ratio of at leastabout 3:2, as determined by x-ray diffraction (ASTM D 3720-78). Thetitania supports preferably contain a rutile:anatase ratio of from about3:2 to about 100:1, or greater, more preferably from about 4:1 to about100:1, or greater. The surface area of such forms of titania are lessthan about 50 m²/g. These weight concentrations of rutile providegenerally optimum activity, and C₁₀₊ hydrocarbon selectivity withoutsignificant gas and CO₂ make.

The prepared catalyst as a final step is dried by heating at atemperature above about 20° C., preferably between 20° C. and 125° C.,in the presence of nitrogen or oxygen, or both, in an air stream orunder vacuum. It is necessary to activate the catalyst prior to use.Preferably, the catalyst is contacted with oxygen, air, or otheroxygen-containing gas at temperature sufficient to oxidize the cobaltand convert the cobalt to Co₃O₄. Temperatures ranging above about 150°C., and preferably above about 200° C. are satisfactory to convert thecobalt to the oxide, but temperatures above about 500° C. are to beavoided unless necessary for regeneration of a severely deactivatedcatalyst. Suitably, the oxidation of the cobalt is achieved attemperatures ranging from about 150° C. to about 300° C. The metal, ormetals, contained on the catalyst are then reduced. Reduction isperformed by contact of the catalyst, whether or not previouslyoxidized, with a reducing gas, suitably with hydrogen orhydrogen-containing gas stream at temperatures above about 200° C.;preferably above about 250° C. Suitably, the catalyst is reduced attemperatures ranging from about 200° C. to about 500° C. for periodsranging from about 0.5 to about 24 hours at pressures ranging fromambient to about 40 atmospheres. A gas containing hydrogen and inertcomponents in admixture is satisfactory for use in carrying out thereduction.

The catalysts of this invention can be regenerated, and reactivated torestore their initial activity and selectivity after use by washing thecatalyst with a hydrocarbon solvent, or by stripping with a gas.Preferably the catalyst is stripped with a gas, most preferably withhydrogen, or a gas which is inert or non-reactive at strippingconditions such as nitrogen, carbon dioxide, or methane. The strippingremoves the hydrocarbons which are liquid at reaction conditions. Gasstripping can be performed at substantially the same temperatures andpressures at which the reaction is carried out. Pressures can be lower,however, as low as atmospheric or even a vacuum. Temperatures can thusrange from about 160° C. to about 290° C., preferably from about 190° C.to about 260° C., and pressures from below atmospheric to about 600psig, preferably from about 140 psig to about 400 psig. If it isnecessary to remove coke from the catalyst, the catalyst can becontacted with a dilute oxygen-containing gas and the coke burned fromthe catalyst at controlled temperature below the sintering temperatureof the catalyst. Most of the coke can be readily removed in this way.The catalyst is then reactivated, reduced, and made ready for use bytreatment with hydrogen or hydrogen-containing gas with a freshcatalyst.

The invention will be more fully understood by reference to thefollowing examples and demonstrations which present comparative dataillustrating its more salient features.

The catalysts of this invention are disclosed in the following examplesand demonstrations as Catalysts Nos. 14-21, and 24. These are catalystswhich have surface films falling within the required range ofthicknesses, and the surface film contains the required cobalt metalloadings. It will be observed that Catalysts No. 14-21 were formed by aprocess wherein a heated particulate TiO₂ substrate was repetitivelycontacted with a dilute spray solution containing both the cobalt andrhenium which was deposited as a thin surface layer, or film, upon theparticles. Catalyst 24 was prepared similarly but with an SiO₂ particle.Catalysts Nos. 14-21 and 24 are contrasted in a series of synthesis gasconversion runs with Catalysts Nos. 1-8 and 22, catalysts wherein themetals are uniformly dispersed throughout TiO₂ or SiO₂ (No. 22) supportparticles, Catalysts Nos. 9-13, also “rim” catalysts but catalystswherein the surface films, or rims, are too thick (Catalysts Nos.11-13), however prepared, or do not contain an adequate cobalt metalloading within the surface film, or rim (Catalysts Nos. 9 and 23).Catalyst 25 is run at 220° C. for comparison with Catalyst 24. Thehigher temperature operation shows increased productivity butsignificantly higher methane production. It is clear that at highproductivities the catalysts formed from the uniformly impregnated TiO₂and SiO₂ spheres produce high methane. Moreover, even wherein a film ofthe catalytic metal is formed on the surface of the particles, it isessential that the surface film, or rim of cobalt be very thin and alsocontain an adequate loading of cobalt in the film. This is necessary tomaximize reaction of the H₂ and CO at the surface of the particlewherein the cobalt metal reaction sites are located, whilesimultaneously reactions within the catalyst but outside the metal filmor rim are suppressed to maximize productivity, and lower methaneselectivity. The following data thus show that the catalysts of thisinvention, i.e., Catalysts Nos. 14-21 and 24 can be employed atproductivities above 150 hr⁻¹, and indeed at productivities rangingabove 150 hr⁻¹ to 200 hr⁻¹, and greater, to produce no more and evenless methane than is produced by (i) catalysts otherwise similar exceptthat the catalysts contain a thicker surface film, i.e., Catalysts Nos.11-13, or (ii) catalysts which contain an insufficient cobalt metalloading with in a surface film of otherwise acceptable thinness, i.e.,Catalyst Nos. 9 and 23. The data show that the catalysts of thisinvention at productivities ranging above about 150 hr⁻¹ to about 200hr³¹ ¹, and greater, at 200° C. can be employed to produce liquidhydrocarbons at methane levels well below 10 mole percent with TiO₂ andless than 15 mole percent with SiO₂.

EXAMPLES 1-8

A series of 21 different catalysts were prepared from titania. TiO₂, and3 different catalysts from SiO₂, both supplied by a catalystmanufacturer in spherical form; the supports having the followingphysical properties, to wit:

TiO₂ (1 mm average diameter)

86-95% TiO₂ rutile content (by ASTM D 3720-78 test)

14-17 m²/g BET surface area

0.11-0.16 cc/g pore volume (by mercury intrusion).

SiO₂ 2.5 mm average diameter 244 m²/g BET surface area 0.96 cc/g porevolume (by nitrogen adsorption)

In the catalyst preparations, portions of the TiO₂ spheres wereimpregnated with cobalt nitrate and perrhenic acid via severalimpregnation techniques as subsequently described. In each instance,after drying in vacuo at 125°-185° C., the catalysts were calcined inflowing air at 250°-500° C. for three hours. A first series of catalysts(Catalyst Nos. 1-8) were prepared wherein TiO₂ spheres were uniformlyimpregnated, and these catalysts then used in a series of base runs(Table 1). Catalyst Nos. 9-11 (Table 2) and 12-21 (Table 3) wereprepared such that the metals were deposited on the outside surface ofthe spheres to provide a shell, film or rim. Catalysts Nos. 22-25 wereprepared with 2.5 mm SiO₂ particles (Table 4). Catalyst No. 22 was afully impregnated SiO₂ particle while Catalysts 23-25 were rim typecatalysts prepared by spraying in a manner similar to that for CatalystNos. 14-21. Catalyst No. 23 had insufficient cobalt loading to produceadequate productivity. The thicknesses of the catalyst rim, or outershell, were determined in each instance by Electron Microprobe Analysis.Runs were made with these catalysts each being contacted with synthesisgas at similar conditions and comparisons (except for Catalyst No. 25run at 220° C.) then made with those employed to provide the base runs.

Catalyst Nos. 1-8, described in Table 1, were prepared as uniformlyimpregnated catalysts to wit: A series of uniformly impregnated TiO₂spheres were prepared by immersing the TiO₂ spheres in acetone solutionsof cobalt nitrate and perrhenic acid, evaporating off the solutions, andthen drying and calcining the impregnated spheres. The Co and Reloadings, expressed as gms metal per cc of catalyst on a dry basis,deposited upon each of the catalysts are given in the second and thirdcolumns of Table 1.

Catalysts No. 9-11 were prepared to contain an outer rim or shell. Thesecatalysts were prepared by a liquid displacement method which involvesfirst soaking the TiO₂ in a water-immiscible liquid, draining off theexcess liquid, and then dipping the wet spheres into a concentratedaqueous solution of cobalt nitrate (0.24 g Co/ml) and perrhenic acid(0.02 g Re/ml). Contact with the metal salt solution is limited to avery short period of time, during which the solution displaces thepre-soak liquid from the outer surface of the support particles. Therim-impregnated catalyst is quickly blotted on paper towels and dried ina vacuum oven at 140° C. Results are summarized in Table 2. The secondcolumn of Table2 thus identifies the presoak liquid, the third columnthe displacement time in minutes, the fourth and fifth columns the gCo/cc and g Re/cc, respectively, and the sixth column the rim thicknessor thickness of the outer metal shell in microns.

Catalysts Nos. 12-21, described in Table 3, were prepared to have metalshells or rims by use of a series of spray techniques. TiO₂ spheres werespread out on a wire screen and preheated in a vacuum oven at varioustemperatures. The hot spheres were removed from the oven, sprayed with asmall amount of metal salt solution, and returned without delay to theoven where drying and partial decomposition of the cobalt nitrate saltoccurred. The spraying sequence was repeated several times in order toimpregnate a thin outer layer or rim of Co-Re onto the support.Preparative details are as follows:

Three solutions I, II and III, each constituted of a different solvent,and having specific concentrations of cobalt nitrate and perrhenic acidwere employed in a series of spraying procedures. The three solutionsare constituted as follows:

Cobalt Nitrate Perrhenic Acid Solution Concentration ConcentrationNumber g Co/ml g Re/ml Solvent I 0.12 0.01 20% H₂O 80% Acetone II 0.120.03 H₂O III 0.12 0.01 Acetone

Five separate procedures, Procedures A, B, C, D and E, respectively,employing each of these three solutions, were employed to preparecatalysts, as follows:

A: 30 ml of Solution I added to 50 g TiO₂ spheres in 5 sprayings

B: 30 ml of Solution I added to 50 g TiO₂ spheres in 3 sprayings

C: 25 ml of Solution I added to 50 g TiO₂ spheres in 5 sprayings

D: 50 ml of Solution II added to 100 g TiO₂ spheres in 5 sprayings

E: 25 ml of Solution III added to 50 g TiO₂ spheres in 5 sprayings

Reference is made to Table 3. The procedure employed in spray coatingthe respective catalyst is identified in the second column of saidtable, and the TiO₂ pre-heat temperature is given in the third column ofsaid table. The g Co/cc and g Re/cc of each catalyst is given in Columns4 and 5, respectively, and the thickness of the catalyst rim is given inmicrons in the sixth column of the table.

The catalysts were diluted, in each instance, with equal volumes of TiO₂or SiO₂ spheres to minimize temperature gradients, and the catalystmixture then charged into a small fixed bed reactor unit. In preparationfor conducting a run, the catalysts were activated by reduction withhydrogen at 450° C., at atmospheric pressure for one hour. Synthesis gaswith a composition of 64% H₂₋₃₂% CO-4% Ne was then converted over theactivated catalyst at 200° C. (or 220° C. for Catalyst No. 25), 280 psigfor a test period of at least 20 hours. Gas hourly space velocities(GHSV) as given in each of the tables, represent the flow rate at 22° C.and atmospheric pressure passed over the volume of catalyst, excludingthe diluent. Samples of the exit gas were periodically analyzed by aschromatography to determine the extent of CO conversion and theselectivity to methane, expressed as the moles of CH₄ formed per 100moles of CO converted. Selectivity to C₄₋ expressed as the wt % of C₄-in the hydrocarbon product, was calculated from the methane selectivitydata using an empirical correlation developed from data obtained in asmall pilot plant. A productivity figure is also given for runs madewith each of these catalysts, productivity being defined as the productof the values represented by the space velocity, the CO fraction in thefeed and the fraction of the CO converted; the productivity being thevolume CO measured at 22° C. and atmospheric pressure converted per hourper volume of catalyst.

TABLE 1 UNIFORMLY IMPREGNATED CATALYSTS, AND GAS CONVERSION RUNS MADETHEREWITH Catalyst Wt. % Wt. % % Co Produc- Mol. % Wt. % Number g Co/ccg Rc/cc GHSV Conv. tivity CH₄ C⁴⁻ 1 0.0392 0.0034 200 67 43 5.4 9.4 20.0617 0.0046 750 50 120 10.5 16.9 3 0.1003 0.0080 500 80 128 11.1 17.74 0.0743 0.0056 750 64 154 11.5 18.3 5 0.0796 0.0050 750 71 170 13.120.7 6 0.1014 0.0084 750 77 185 13.9 21.8 7 0.0925 0.0066 750 77 18513.9 20.9 8 0.1025 0.0068 1000 65 208 14.7 23.0

TABLE 2 RIM CATALYSTS PREPARED BY LIQUID DISPLACEMENT METHOD, AND GASCONVERSION RUNS MADE THEREWITH Displacement Rim Catalyst Presoak TimeThickness % CO Produc- Mol. % Wt. % Number Liquid Minutes g Co/cc gRc/cc Microns GHSV Conv. tivity CH₄ C⁴⁻ 9 98% Mesitylene/ 2 0.02640.0023 140⁽¹⁾ 250 83 66 6.5 11.0 2% n-Heptanol 10 98% Mesitylene/ 10.0373 0.0031 200⁽¹⁾ 500 66 106 7.6 12.6 2%-2-Ethyl-1-hexanol 11 98%Mesitylene/ 2 0.0459 0.0038 320⁽²⁾ 500 70 112 9.3 15.12%-2-Ethyl-1-hexanol ⁽¹⁾The rim thickness of these catalysts fallswithin the acceptable range. An insufficient concentration of the totalmetals deposited on the TiO₂ spheres, however, is contained within therim. ⁽²⁾Adequate metal concentration but large rim thickness lead tohigher but still adequate methane and inadequate productivity.

TABLE 3 RIM CATALYSTS PREPARED BY SPRAYING METHOD, AND GAS CONVERSIONRUNS MADE THEREWITH Cat- TiO₂ Rim alysts Pre-Heat Thickness % Co Mol. %Wt. % Number Procedure Temp. ° C. g Co/cc g Rc/cc Microns GMSV Conv.Productivity CH₄ C⁴⁻ 12 A 140 0.0624 0.0050 250 400 85 109 8.9 14.5 13 B125 0.0818 0.0068 300 750 85 204 11.8 18.8 14 C 140 0.0531 00045 140 80068 174 8.2 13.3 15 C 140 0.0613 0.0050 150 800 71 182 8.2 13.5 16 C 1400.0739 0.0070 130 800 81 207 8.7 14.2 17 D 185 0.0507 0.0125 160 800 68174 9.2 15.0 18 E 185 0.0549 0.0049 90 800 68 174 6.5 11.0 19 C 1850.0483 0.0043 70 800 64 164 6.7 11.3 20 C 185 0.0474 0.0033 90 800 65166 7.5 12.5 21 C 185 0.0603 0.0046 60 800 74 189 7.2 12.0

TABLE 4 CATALYSTS MADE FROM SiO₂ PARTICLES (2.5 MM DIA.) AND GASCONVERSION RUNS THEREWITH Rim Catalyst Wt. % Wt. % Thickness % Co Mol. %wt % Number g Co/CC Re Microns GHSV Conv. Productivity CH₄ C⁴⁻ 22 .1332.4 ⁽¹⁾ 600 71 136 19.5 30.0 23 .035 0.4 118 400 67 86 5.7 9.8 24 .0671.5 192 800 71 182 13.4 21.9 25⁽²⁾ .067 1.5 192 1100 76 268 21.9 33.5⁽¹⁾Uniformly impregnated, no rim present ⁽²⁾Run at 220° C.

The effectiveness of these catalysts for conducting synthesis gasreactions is best illustrated by comparison of the methane selectivityat given productivity with Catalysts 1-8 (Table 1), the catalysts formedby the uniform impregnation of the metals throughout the TiO₂ catalystspheres, and Catalysts 9-11 (Table 2) and 12-21 (Table 3), thosecatalysts wherein the metals were deposited as a shell, or rim, upon theoutside of the TiO₂ catalyst spheres. The same type of comparison isthen made between certain of the latter class of catalysts, and others,which also differ one from another dependent upon the thickness of themetals-containing rim. These data are best graphically illustrated forready, visual comparison. Reference is thus made to FIG. 1 wherein themethane selectivity produced at given productivity is plotted for eachof the twenty-one catalysts described by reference to Tables 1-3. Asolid black data point is plotted for each of Catalysts Nos. 1-8, formedfrom the uniformly impregnated TiO₂ spheres, and each data point isidentified by catalyst number. An open circle is plotted for each datapoint representative of Catalysts Nos. 9-21, each is identified bycatalyst number, and the rim thickness of the catalyst is given. Thebehavior of many of these catalysts (i.e., Catalysts 9-13), it will beobserved is somewhat analogous to that of Catalysts Nos. 1-8. CatalystsNos. 14-21, however, behave quite differently from either of the othergroups of catalysts, i.e., Catalysts Nos. 1-8 or Catalysts 9-13. Themethane selectivity is thus relatively low for Catalysts Nos. 9-12, butat the same time the productivities of these catalysts are quite low. Onthe other hand, the productivities of Catalysts Nos. 2-8 are higher thanthose of Catalysts Nos. 9-12, but at the same time these catalystsproduce copious amounts of methane. In striking contrast to either ofthese groups of catalysts, Catalysts Nos. 14-21, all of which fallwithin the “box” depicted on the figure, provide very highproductivities and, at the same time, low methane selectivities.Catalysts Nos. 14-21 thus differ profoundly from any of Catalysts Nos.1-13 in their behavior, and in that the metals components of thesecatalysts is packed into a very thin rim, or shell, on the surface ofthe TiO₂ support.

These data thus show that a constant temperature as productivityincreases so too does methane selectivity for both the groups ofcatalyst represented by Catalysts Nos. 1-8, the uniformly impregnatedcatalysts, and Catalysts Nos. 11-13 which have relatively thick outershells or rims. Thus, methane selectivity increases in proportion to themetal loadings when the metals are dispersed throughout the support orcarrier portion of the catalyst. Methane selectivity also increases inproportion to the thickness of the catalyst rim. Albeit the methaneselectivities obtained with Catalysts Nos. 9-12 are within acceptableranges, the productivities obtained with these catalysts are quite low.Catalyst No. 13 has adequate productivity but makes significant methane.Catalyst No. 9, although it has a thin metallic rim and provides lowmethane selectivity, its productivity is quite poor because of aninsufficient loading of metals within the rim. Catalyst Nos. 14-21 whichhave thin metallic rims and relatively high metals loadings within therims, on the other hand, provide low methane selectivities and highproductivities.

The results observed with Catalyst Nos. 1-13 and 22 are consistent withthe onset of a significant diffusion limitation at the higherproductivities, which intensifies as the catalyst become more active. Insharp contrast, however, catalysts which have cobalt rim thicknesses ofless than about 200 microns, notably from about 20 microns to about 180microns, can produce at high productivities (i.e., at least about 150hr⁻¹, or even at least about 200 hr⁻¹) very low methane selectivities.Catalysts with very thin rims counteract the diffusion problem bylimiting reaction to the outer surface of the catalyst wherein lies thecatalytically active metal components. The catalysts of this inventionthus provide a means of operating at high productivity levels with lowmethane selectivities. Methane selectivities are reduced at higher andhigher productivities, as the rim thickness is made smaller and smaller.When productivity is increased beyond 150 hr⁻¹, 200° C. to at leastabout 200 hr⁻¹ the metals rim should be no more than about 180 micronsthick, and the rim can be even thinner. This region of operation, thebest balance between activity and selectivity, is represented in FIGS. 1and 2 by the area enclosed within the box formed by the dashed lines.FIG. 2 presents the performance of SiO₂ catalysts and Catalyst No. 24illustrates this invention. The methane yield is slightly higher thanfor TiO₂ particles, owing to intrinsic qualities of TiO₂ catalysts.Nevertheless, the requirements for the best balance between productivityand selectivity are the same for SiO₂ catalysts as for TiO₂ catalysts,e.g., adequate metal loading in a relatively thin rim. Catalyst No. 23,although it has a thin rim and provides low methane selectivity, itsproductivity is quite poor because of an insufficient loading of metalswithin the rim. FIG. 2 also includes calculated numbers on productivityfrom a EPA 178008 based on a 2.5 mm particle all of which shownunacceptably high levels of methane yield because of the relativelythick rims encountered in that case.

These data further show that the catalysts of this invention (CatalystNos. 14-21 and 24) can be readily prepared by the process ofsequentially, or repetitively spraying hot, or preheated supportparticles with solutions containing compounds or salts of the metals.Suitably, the TiO₂ or SiO₂ substrate is preheated to temperatures of atleast about 140° C. to about 185° C., prior to or at the time of contactthereof with the solution. Higher temperatures can be employed, buttemperatures below about 140° C. do not produce a sufficiently thin rimof the metals on the catalyst support. The repetitive spraying techniqueis shown to be superior to liquid displacement technique used to prepareCatalyst Nos. 9-10 and 23 wherein only low cobalt loadings weredeposited in a single contact because of the cobalt concentration limitin the displacing solution. Longer displacement time increases the metalloading but produces a thicker rim as shown by Catalyst No. 11 comparedwith Catalyst No. 10. The spray technique provides especially gooddispersion of the metals as a thin rim at the outer surface of thesupport particles by application of the metals a little at a time bymultiple impregnations. Loading the metals onto the catalysts in thismanner increases the activity of the catalysts and provides higherproductivity.

These reactions can be conducted with the catalysts of the presentinvention in any Fischer-Tropsch reactor system, e.g., fixed bed,fluidized bed, or other reactors, with or without the recycle of anyunconverted gas and/or liquid product. The C₁₀₊ product that is obtainedis an admixture of linear paraffins and olefins which can be furtherrefined and upgraded to high quality middle distillate fuels, or suchother products as mogas, diesel fuel, jet fuel and the like. A premiumgrade middle distillate fuel of carbon number ranging from about C₁₀ toabout C₂₀ can also be produced from the C₁₀₊ hydrocarbon product. Thecatalyst is constituted of cobalt supported on a carrier, preferablytitania, and especially cobalt supported on a rutile form of TiO₂ orrutile-titania-containing support which can contain other materials suchas SiO₂, MgO, ZrO₂, Al₂O₃. The catalyst is preferably reduced with aH₂-containing gas at start-up.

EXAMPLE 9

About 14,500 lbs of finished catalyst was obtained by doubleimpregnating a spray-dried support made from Degussa P-25 titania. Thetitania was spray-dried with an alumina sol binder. Product with anaverage particle size of about 45 microns was made in very high yield(97%). The support was then converted into the rutile form bycalcination at high temperature in a 30″×50″ rotary calciner.Impregnation with an aqueous solution of cobalt nitrate and perrhenicacid was performed batch-wise in a 5 ft³ V-blender. The nitrate salt wasdecomposed by calcining the catalyst in the larger rotary at about 450°C. A second pass through impregnation and calcination produced thefinished catalyst.

High resolution imaging and EDS analysis of a cross-sectional view ofthe above catalyst is shown in FIG. 3.

It is apparent that various modifications and changes can be madewithout departing the spirit and scope of the present invention.

What is claimed is:
 1. A process useful for the conversion of synthesisgas to liquid hydrocarbons and less than about 10 mole % methane whichcomprises contacting at reaction conditions a feed comprised of carbonmonoxide and hydrogen, in H₂:CO molar ratio equal to or greater thanabout 0.5:1 at total pressure equal to or greater than about 80 psig,over a catalyst composition having a productivity of at least 150 hr⁻¹at 200° C. and which comprises cobalt dispersed as a catalyticallyactive layer upon the outer surface of an inorganic oxide support of athickness of less than about 200 microns, with the loading of cobalt atleast about 0.04 g/cc in said catalytically active layer, calculated asmetallic cobalt per packed bulk volume of catalyst.
 2. The process ofclaim 1 wherein the molar ratio of H₂:CO ranges from about 1.7:1 toabout 2.5:1.
 3. The process of claim 2 wherein the total pressure of thereaction ranges from about 140 psig to about 400 psig.
 4. The process ofclaim 1 wherein the reaction conditions are defined within ranges asfollows: H₂:CO mole ratio about 1.7:1 to 2.5:1 Gas Hourly SpaceVelocities, V/Hr/V about 300 to 1500 Temperature, ° C. about 190 to 220Total Pressure, psig about 140 to 400


5. The process of claim 1 wherein the catalytically active surface layerof the catalyst is of average thickness ranging from about 5 microns toabout 200 microns with the cobalt loading ranging being at least about0.04 g/cc in said catalytically active surface layer.
 6. The process ofclaim 1 wherein the catalyst further comprises rhenium rheniumconstitutes part of the catalytically active surface layer of thecatalyst.
 7. The process of claim 1 wherein the catalyst furthercomprises hafnium which constitutes part of the catalytically activesurface layer of the catalyst.
 8. The process of claim 1 wherein thesupport is comprised of silica or titania.
 9. A process for theconversion of synthesis gas to C₁₀₊ hydrocarbons which comprisescontacting at reaction conditions a feed comprised of an admixture ofcarbon monoxide and hydrogen, in H₂:CO molar ratio equal to or greaterthan about 1.71 at total pressure equal to or greater than about 80psig, over a catalyst composition which comprises cobalt dispersed as acatalytically active layer upon the outer surface of a silica or titaniacontaining support, said active layer being of a thickness of less than200 microns, and with sufficient cobalt loading to produce aproductivity of at least about 150 hr⁻¹ at 200° C. and convert tomethane less than 10 mole percent of the carbon monoxide converted. 10.The process of claim 9 wherein the support is comprised predominantly ofsilica.
 11. The process of claim 1 wherein said process is a slurry-bedsynthesis gas conversion process and said catalyst having a particlesize diameter of about 10 microns to about 1 mm.
 12. The process ofclaim 1 wherein said liquid hydrocarbon comprises a high qualitydistillate fuel.
 13. The process of claim 1 wherein said liquidhydrocarbon comprises C₁₀₊ hydrocarbons.
 14. The process of claim 13wherein said C₁₀₊ hydrocarbons comprise C ₁₀₊ linear paraffins.
 15. Theprocess of claim 13 comprising the further step of producing a middledistillate fuel from said C₁₀₊ hydrocarbons.
 16. The process of claim 15wherein said middle distillate fuel comprises a diesel fuel.
 17. Theprocess of claim 15 wherein said middle distillate fuel comprises a C₁₀-C ₂₀ product.
 18. The process of claim 15 wherein said middledistillate fuel comprises a jet fuel.
 19. The process of claim 13including upgrading said C₁₀₊ hydrocarbons.
 20. The process of claim 19including upgrading said C₁₀₊ hydrocarbons to a diesel fuel.
 21. Theprocess of claim 19 including upgrading said C₁₀₊ hydrocarbons to a jetfuel.
 22. The process of claim 9 wherein said C₁₀₊ hydrocarbons compriseC ₁₀₊ linear paraffins.
 23. The process of claim 9 comprising thefurther step of producing a middle distillate fuel from said C₁₀₊hydrocarbons.
 24. The process of claim 23 wherein said middle distillatefuel comprises a diesel fuel.
 25. The process of claim 23 wherein saidmiddle distillate fuel comprises a jet fuel.
 26. The process of claim 23wherein said middle distillate fuel comprises a C₁₀ -C ₂₀ product. 27.The process of claim 9 including upgrading said C₁₀₊ hydrocarbons. 28.The process of claim 27 including upgrading said C₁₀₊ hydrocarbons to adiesel fuel.
 29. The process of claim 27 including upgrading said C₁₀₊hydrocarbons to a jet fuel.